To solve a problem that, in a conventional electric heater type preheating device, since heating capacity is low and a temperature increase speed is not so fast, when heating capacity is increased, a heater is increased in size and as a result, the whole of a device is increased in size; a temperature increasing time is needed for a long time, an ingot is heated to temperature higher than necessary temperature, and a trouble is apt to occurs; and since most of a conveyance line is covered by an electric heater, a charge opening for an ingot is normally limited to one spot and it takes a long time to effect charging.

The preheating device for the ingot is proposed that a preheat chamber surrounded by a wall is formed at a part of a conveyance line situated at a part of a holding part 8 for the ingot 7, and constitution is such that the ingot is conveyed through the preheating chamber, and a surface combustion burner 14 is situated in a preheating chamber and in the opposite position of the ingot conveyed through the preheating chamber.